<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">

        var a = "12";
        var b = 12;

        alert( a == b ); // true
        alert( a === b ); // false

    </script>
</head>
<body>

</body>
</html>